<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title>对话框</title>
		<link rel="stylesheet" type="text/css" href="css/reset-min.css"/>
		<style type="text/css">
			.box{
				width: 400px;
				height: 200px;
				border: 1px solid;
				border-radius: 50%;
				text-align: center;
				font: 30px helvetica;
				/* 如果要修改行高，line-height必须写在font下面。因为font有个默认行高 */
				line-height: 200px;
				position: relative;
			}
			/* 使用伪元素 */
			.box:before{
				content: "";
				/* 设置为块级元素，才能设置宽高 */
				display: block;
				width: 80px;
				height: 80px;
				border: 1px solid;
				border-radius: 50%;
				position: absolute;
				right: -40px;
				bottom: -40px;
			}
			.box:after{
				content: "";
				display: block;
				width: 60px;
				height: 60px;
				border: 1px solid;
				border-radius: 50%;
				position: absolute;
				right: -100px;
				bottom: -100px;
			}
		</style>
		
	</head>
	<body>
		<div class="box">
			大家好，欢迎入坑前端
		</div>
	</body>
</html>
